1. Field of the Invention
This invention relates to guiding waves of electromagnetic energy and more particularly to guiding energy associated with a wave from a single signal source to a plurality of loads and from a plurality of signal sources to a single load.
2. Description of the Prior Art
An amplification device is usually incapable of providing a high power level to a load at microwave frequencies. A plurality of similar devices are typically connected in parallel whereby each of the plurality of devices provides a portion of the power to the load.
One well known type of single port device is a diode, such as either the Gunn or IMPATT type, or a pumped varactor, which has a negative resistance characteristic. A plurality of the diodes are typically included in what is known as a reflection amplifier. Because of the negative resistance, when input power is provided to the reflection amplifier, there is a reflection therefrom of output power that exceeds the input power. The reflection amplifier has a power gain that is a maximum when the negative resistance of the reflection amplifier has an amplitude that approximately matches the amplitude of the characteristic impedance of a transmission line, such as a waveguide, that couples power to and from the reflection amplifier.
The amplitude of the impedance of the diode typically is low in comparison with the characteristic impedance. Because the reflection amplifier includes a plurality of diodes that are connected in parallel, the reflection amplifier has an impedance with an amplitude that is much lower than the amplitude of the characteristic impedance. Accordingly, there is usually a severe mismatch between the impedance of the reflection amplifier and the characteristic impedance. Hence, there is a need for a reflection amplifier that has an impedance with an amplitude which is easily matched to a waveguide.
Similarly, another well known type of device, a transistor, has input and output impedances that are low in comparison with the characteristic impedance. A power amplifier usually includes a plurality of transistors connected in parallel.
Therefore, the power amplifier has input and output impedances that are much lower than the characteristic impedance. Accordingly, there is usually a severe mismatch between the input and output impedance of the power amplifier and the characteristic impedance.
An impedance mismatch is obviated by coupling an amplification device to the waveguide through an impedance transformation device. The transformation device has a bandwidth that is inversely related to a ratio (called an impedance transformation ratio) of the characteristic impedance to the impedance of the amplification device. Therefore, the transformation device introduces a substantial limitation on the bandwidth of power transmitted therethrough. Hence, there is a need for a power amplifier that can be used without introducing such a bandwidth limitation.